Vector 4 - Page 108

Baud Rate Chart
Baud Rate Count Value
110 0470H
150 0341H
300 - 01A1H
600 00DOH
1200 0068H
2400 0034H
4800 001AH
9600 000DH
C.. Interrupt generation
VECTOR 4
TECHNICAL INFORMATION
The 8253 programmable timer is also used to generate a signal which is
connected to the maskable interrupt line on the Z80B. For the Extended CP/M
Operating System this represents a pulse generated every 20 milliseconds (60
Hz).
The operating system uses this signal for keyboard servicing and tasking
routines.
This interrupt timing signal (Tp) is configured by outputs to ports 10H and 13H
(control port).
- Outputting 30H to port 13H (initialization)
This is accomplished by:
- Outputting appropriate delay count value to port 10H.
09-01-82
7200-0001
II 5-17